The possibility of obtaining sources of metallic ions of atomic dimensions has been investigated by E. W. Mueller and T. T. Tsong. Progress in Surface Science, Vol. 1, pag. 1 (1974) but its physical realization has not been possible up to now. When a large electric field (a few tens of volt per nanometer) is applied to a metallic surface the phenomena of metallic ion evaporation by field is observed. However at low temperatures (liquid nitrogen (LN)) the number of emitted ions is very small due to the fact that the surface diffusion is small and the beam although originated in a single atomic site is not useful. If the temperature is increased too much the ions come out from many sites and the beam is not coherent and not focussed. At higher temperatures, near to the bulk temperature of melting of the material, the metal became liquid and a beam of ions of macroscopic dimensions can be obtained, with the characteristics of a hydrodynamic fluid. This is the basis of the beams used now a days and are known as Taylor cones (G. I. Taylor, Proc. Roy. Soc. London A313, 453 , (1969)).